This invention relates generally to wiper assemblies for the bearers of printing press rolls and more particularly to an improved wiper assembly mounted to an extended arm for controlled bearer engagement.
Printing press rolls are provided, at each end, with cylindrical bearers which directly engage each other and have substantially fixed parallel axes of rotation.
The conventional method of cleaning such bearers is by the application of a felt pad to the surface of the bearers, the pad being held in constant engagement with the bearers during rotation of the printing rolls. This is an unsatisfactory arrangement for several reasons. The most important of these results from the fact that such a constant contact system generates a considerable amount of heat. This heat causes the bearers to expand diametrically and, because of the fixed axes, the growth of the bearers increases the load on the bearers which compounds the heat generation problem and can result in bearing fatigue. Another result of bearer growth due to heat generation is that additional power is required to drive the system resulting in higher energy costs and transmission wear.
In addition to the above, when the bearers experience diametrical growth there is a tendency for the printing cylinders to be forced apart causing dot deterioration and a corresponding deterioration in print quality.
Heat generation in the bearers also causes heat generation in the cylinders resulting in undue water evaporation resulting in an undesirable condition known as scumming which also lowers print quality.
Another problem resulting from providing constant contact bearer wipers is that when the presses are at rest the wipers are engaged for extended periods against the bearer surface which is conducive to bearer corrosion.
The prior art reveals that attempts have been made to correct the above problems but the proposed solutions are evidently either ineffective or expensive since the constant contact wiper is still widely used. Of the known prior patents the following are of interest. U.S. Pat. No. 4,015,307 discloses a housing carrying a rotatable absorbent wiper roller which is moved hydraulically into engagement with a cylindrical surface. U.S. Pat No. 4,162,652 discloses a spring-loaded and hinged sponge and scraper assembly. U.S. Pat. No. 3,822,642 discloses a pivotally mounted scraper which is moved into engagement with a bearing surface hydraulically.
The present bearer wiper assembly solves the problems outlined above in a manner not revealed by the known prior art.